River mouth mobility during the Ist millennium BCE: The case of the Po and the Etruscan city of Spina (Ferrara, Italy)

Résumé En

During the first millennium BCE, the main mouth of the Po River was located at the central part of the delta in the area of Comacchio (Province of Ferrara). The river mouth formed a promontory with several beach-ridges well preserved and visible on aerial photographs. The fortuitous discovery of the Etruscan site of Spina in the first part of the 20th century in this deltaic context raises many questions about the resilience of the city in this geomorphological configuration. The connections with the Mediterranean basin, the Po Valley and the Alps and Apennines mountains makes it a privileged commercial hub. For several decades, the issue of proximity to the river and the coast has been central to understanding its commercial dynamism but also the risks that may lead to the decline of this short-lived city (6th-3rd century BCE). This ancient deltaic lobe has been little explored regarding the Late Holocene and offers limited dates except for major trends obtained by interpolation. The chronology of the local succession of the ancient coastline is based on tangible archaeological evidence providing a coastline in the archaeological sense and a terminus ante quem. However, numerical geochronological tools have never been used to date these deposits. A French-Italian core drilling campaign was conducted as part of a project called “EOS-Etruscan on the Sea” (2020-on) in 2022. This new sedimentary data, based on an innovative sampling strategy with systematic drillings on the paleochannel and the beach-ridges, will be studied by a multiproxy approach combining several dating techniques (14C, OSL, and portable OSL reader) with various sedimentological analyses. We explore, thanks to a high-resolution analysis, the river mouth deposits over time and space, as well as their relationships with the city.